The industry trend goes towards high capacity scalable MSC servers. A typical architecture for such a system is a blade cluster structure. Transmission lines that carry payload are terminated in media gateways (MGw), and the switching of these resources is controlled by the MSC server.
Time division multiplex terminations (TDM terminations) are not very well suited to be controlled by a blade cluster system because neither the call controlling signaling nor the media gateway control signaling provides support for a multi-blade architecture. Before a termination can be used for a call, coordination of exclusive usage must be performed between the MSC blades. The seizure of terminations is coordinated by the media gateway. There is no need for inter-blade coordination on the MSC server side. Signaling messages need to be routed to the blade that handles the respective call. BICC (Bearer Independent Call Control Protocol) uses ephemeral terminations but requires coordination of the call instance codes (CIC) on the MSC server side, since they are a common resource of all blades.
With the existing technology there is no possibility to share TDM terminations and CICs amongst several blades. The range of available TDM circuits and for BICC the range of call instance codes has to be partitioned. Each partition is administratively assigned to a particular MSC blade.
In FIG. 1a such a MSC server known in the art is shown. The switching center server 10 has a blade structure cluster with a plurality of blades 11. For the communication with the media gateway 15 the media gateway is divided into several virtual media gateways 16, each virtual media gateway communicating with one blade 11 of the server. Each physical media gateway needs to be configured with one virtual media gateway for each MSC blade. The partitioning of the resources and the assignment of one blade to one virtual media gateway has several disadvantages. First of all, the configuration of the MSC server is more complex compared with a system that does not need to partition the TDM circuits. If one of the blades in the configuration shown in FIG. 1 fails, the resources assigned to the virtual media gateway cannot be used for call connections. Additionally, when the number of blades is changed, e.g. in order to increase the processing power of the server, the media gateway has to be adapted as well.
In FIG. 1b the external network view for a MSC server having a blade structure as known in the art is shown. The MSC server appears as having a signaling endpoint for each blade. To this end the circuits are partitioned on the different blades. In the example shown the MSC server appears as two servers with two signaling proxies in front. When a new blade is added to the server, the entire system including the virtual media gateways and the partitioning of the resources has to be re-configured.